X-ray phase contrast and absorption imaging for the quantification of transient cavitation in high-speed nozzle flows
X-ray phase contrast and absorption imaging for the quantification of transient cavitation in high-speed nozzle flows
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DOI：
10.1063/5.0038475
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发表时间：
2021-03
影响因子：
4.6
通讯作者：
I. Karathanassis;M. Heidari-Koochi;Q. Zhang;J. Hwang;P. Koukouvinis;J. Wang;M. Gavaises
中科院分区：
文献类型：
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作者：
I. Karathanassis;M. Heidari-Koochi;Q. Zhang;J. Hwang;P. Koukouvinis;J. Wang;M. Gavaises
高通量同步辐射已采用时间分辨的方式来表征不同的拓扑结构的功能和动力学的不同的空化制度所产生的节流孔突然流入收缩。通过X射线相衬和吸收成像获得的射线照片已被捕获在67 890帧每秒。流量位于湍流状态（Re = 35 500），而温和的（CN = 2.0），以完善的（CN = 6.0）空化条件进行了检查，包括云和旋涡空化制度与相关的瞬态功能，如云腔脱落。X射线相衬成像，利用与物质相互作用期间X射线波相位的偏移，在界面区域提供尖锐的折射率梯度。因此，它适用于捕捉瞬态空化结构的精细形态波动。然而，该技术不能提供关于孔内的蒸汽量的信息。这些数据是利用吸收成像获得的，其中光束衰减与散射和折射事件无关，因此可以明确地与视线测量中的投影蒸汽厚度相关。提出了两种方法的组合，因为已经发现，它能够量化的复杂的喷嘴流中产生的蒸汽含量，同时也忠实地说明了动态的高度瞬态空化功能。
High-flux synchrotron radiation has been employed in a time-resolved manner to characterize the distinct topology features and dynamics of different cavitation regimes arising in a throttle orifice with an abrupt flow-entry contraction. Radiographs obtained though both x-ray phase-contrast and absorption imaging have been captured at 67 890 frames per second. The flow lies in the turbulent regime (Re = 35 500), while moderate (CN = 2.0) to well-established (CN = 6.0) cavitation conditions were examined encompassing the cloud and vortical cavitation regimes with pertinent transient features, such as cloud-cavity shedding. X-ray phase-contrast imaging, exploiting the shift in the x-ray wave phase during interactions with matter, offers sharp-refractive index gradients in the interface region. Hence, it is suitable for capturing fine morphological fluctuations of transient cavitation structures. Nevertheless, the technique cannot provide information on the quantity of vapor within the orifice. Such data have been obtained utilizing absorption imaging, where beam attenuation is not associated with scattering and refraction events, and hence can be explicitly correlated with the projected vapor thickness in line-of-sight measurements. A combination of the two methods is proposed as it has been found that it is capable of quantifying the vapor content arising in the complex nozzle flow while also faithfully illustrating the dynamics of the highly transient cavitation features.